I like movies and books where private detectives and police solve mysteries.
I like reading books and watching movies where the main characters are police or/and private detectives.
この場合、次のように言うと良いかと思います。
ーI like movies and books where private detectives and police solve mysteries.
「私立探偵や警察が謎を解く映画や本が好きです」
ーI like reading books and watching movies where the main characters are police or/and private detectives.
「主人公が警察や私立探偵の本を読んだり、映画を見たりするのが好きです」
ご参考まで！
カナダ 
